Fossil fuel is a general term for buried combustible geologic deposits of organic materials, formed from decayed plants and animals that have been converted to crude oil, coal, natural gas, or heavy oils by exposure to heat and pressure in the earth's crust over hundreds of millions of years. Fossil fuels are a finite, non-renewable resource. Increased demand for energy by the global economy has also placed increasing pressure on the cost of hydrocarbons. Aside from energy, many industries, including plastics and chemical manufacturers, rely heavily on the availability of hydrocarbons as a feedstock for their manufacturing processes. Cost-effective alternatives to current sources of supply could help mitigate the upward pressure on energy and these raw material costs.
PCT Pub. No. 2008/151149 describes methods and materials for cultivating microalgae for the production of oil and particularly exemplifies the production of diesel fuel from oil produced by the microalgae Chlorella protothecoides. There remains a need for improved methods for producing oil for fuel, chemicals, foods and other uses, particularly for methods that produce oils with shorter chain length and a higher degree of saturation and without pigments, with greater yield and efficiency. The present invention meets this need.
A polyurethane is a compound that comprises a carbamate (urethane) linkage. Typically, a polyurethane is a polymer of organic units. The polymer is prepared by the reaction of a first organic unit comprising an isocyanate moiety (C(O)N—R1—NC(O)) and a second organic unit comprising a hydroxyl group (HO—R2—OH). A polyurethane can be represented as —[C(O)NH—R1—NHC(O)—O—R2—O—R2—O]m—, wherein the subscript m is a number that denotes the number of monomers contained in the polymer. R1 and R2 can be the same or different, but are typically different. Polyurethanes are used in many different applications including both flexible and rigid materials. Polyurethanes are used in shoes, automobiles, airplanes, bushings, gaskets, adhesives, carpeting, spandex fibers, housing for electronics and the like.